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At least 271 records · Page 15

Conceptual design of an orbital debris collector

The current Lower Earth Orbit (LEO) environment has become overly crowded with space debris. An evaluation of types of debris is presented in order to determine which debris poses the greatest threat to operation in space, and would therefore provide a feasible target for removal. A target meeting these functional requirements was found in the Cosmos C-1B Rocket Body. These launchers are spent space transporters which constitute a very grave risk of collision and fragmentation in LEO. The motion and physical characteristics of these rocket bodies have determined the most feasible method of removal. The proposed Orbital Debris Collector (ODC) device is designed to attach to the Orbital Maneuvering Vehicle (OMV), which provides all propulsion, tracking, and power systems. The OMV/ODC combination, the Rocket Body Retrieval Vehicle (RBRV), will match orbits with the rocket body, use a spin table to match the rotational motion of the debris, capture it, despin it, and remove it from orbit by allowing it to fall into the Earth's atmosphere. A disposal analysis is presented to show how the debris will be deorbited into the Earth's atmosphere. The conceptual means of operation of a sample mission is described.

Odonoghue, Peter↗

Position reporting system using small satellites

A system able to provide position reporting and monitoring services for mobile applications represents a natural complement to the Global Positioning System (GPS) navigation system. The system architecture is defined on the basis of the communications requirements derived by user needs, allowing maximum flexibility in the use of channel capacity, and a very simple and low cost terminal. The payload is sketched, outlining the block modularity and the use of qualified hardware. The global system capacity is also derived. The spacecraft characteristics are defined on the basis of the payload requirements. A small bus optimized for Ariane IV, Delta II vehicles and based on the modularity concept is presented. The design takes full advantage of each launcher with a common basic bus or bus elements for a mass production.

Pavesi, B.↗

Dynamic Control of Aerodynamic Instabilities in Gas Turbine Engines

This lecture discusses the use of closed loop control at the component level to enhance the performance of gas turbine engines. The general theme is the suppression of flow instabilities (rotating stall and surge) through use of feedback, either actively or by means of the aeromechanical coupling provided by tailored structures. The basic concepts that underlie active control of turbomachinery instability, and their experimental demonstration, are first described for a centrifugal compressor. It is shown that the mechanism for stabilization is associated with damping of unsteady perturbations in the compression system, and the steady-state performance can thus remain virtually unaltered. Control of instability using a tailored structure is then discussed, along with experimental results illustrating the flow range extension achievable using this technique. A considerably more complex problem is presented by active control or rotating stall where the multi-dimensional features mean that distributed sensing and actuation are required. In addition, there are basic questions concerning unsteady fluid mechanics; these imply the need to resolve issues connected with identification of suitable signals as well as with definition of appropriate wave launchers for implementing the feedback. These issues are discussed and the results of initial successful demonstrations of active control of rotating stall in a single-stage and a three-stage axial compressor are presented. The lecture concludes with suggestions for future research on dynamic control of gas turbine engines.

E M Greitzer↗

Planet-B: A Japanese Mars aeronomy observer

An introduction is given to a Japanese Mars mission (Planet-B) which is being planned at the Institute of Space and Aeronautical Science (ISAS), Japan. Planet-B aims to study the upper atmosphere of Mars and its interaction with the solar wind. The launch of Planet-B is planned for 1996 on a new launcher, M-L, which is being developed at ISAS. In addition to the interaction with the solar wind, the structure of the Martian upper atmosphere is thought to be controlled by the meteorological condition in the lower atmosphere. The orbit of Planet-B was chosen so that it will pass two important regions, the region where the solar wind interacts with the Martian upper atmosphere and the tail region where ion acceleration is taking place. Considering the drag due to the Martian atmosphere, the periapsis altitude of 150 km and apoapsis of 10 Martian radii are planned. The orbit plane will be nearly parallel to the ecliptic plane. The altitude of the spacecraft will be spin stabilized and its spin axis will be controlled to the point of the earth. The dry weight of the spacecraft will be about 250 kg, including the scientific payload which consists of a magnetometer, plasma instruments, HF sounder, UV imaging spectrometer, and lower atmosphere monitor.

Tsuruda, K.↗

Mars exploration advances: Missions to Mars - Mars base

An overview is presented of Mars missions and related planning with attention given to four mission architectures in the light of significant limitations. Planned unpiloted missions are discussed including the Mars Orbital Mapping Mission, the Mars Rover Sample Return, the Mars Aeronomy Orbiter, and the Mars Environmental Survey. General features relevant to the missions are mentioned including launch opportunities, manned-mission phases, and propulsion options. The four mission architectures are set forth and are made up of: (1) the Mars-exploration infrastructures; (2) science emphasis for the moon and Mars; (3) the moon to stay and Mars exploration; and (4) space resource utilization. The possibility of robotic missions to the moon and Mars is touched upon and are concluded to be possible by the end of the century. The ramifications of a Mars base are discussed with specific reference to habitability and base activities, and the human missions are shown to require a heavy-lift launcher and either chemical/aerobrake or nuclear-thermal propulsion system.

Dejarnette, Fred R.↗

A 20-dB quasi-integrated horn antenna

A multimode quasi-integrated dipole-fed horn antenna is presented with a performance comparable to that of waveguide-fed corrugated horn antennas. The antenna has been designed using fullwave analysis and has been fabricated and tested at 91 GHz. The horn has a gain of 20 dB with very symmetric patterns, a Gaussian coupling efficiency of 97 percent, and a cross-polarization level of -22.7 dB. The antenna provides a significant improvement in integrated antenna designs and is suitable for millimeter-wave communication and radar systems and as a Gaussian-beam launcher in quasi-optical receiver systems.

Eleftheriades, George V.↗

National Launch System KSC facilities and operations

The current planning for the launch site ground operations and facilities required at the Kennedy Space Center to accommodate the National Launch System (NLS) are described. Special consideration is given to the program activities associated with reducing costs for ground operations and with the ground operations vehicle processing scenarios for launching the NLS vehicles from KSC. The KSC facilities described include the Payload Encapsulation Facility, the Mobile Launcher Platform, and the Cargo Transfer Vehicle Checkout Facility. Attention is also given to the modifications of existing facilities required to accommodate the NLS facilities and the transportation and handling equipment.

Evans, R. T., Jr.↗

Evaluation of Whipple Bumper shields at 7 and 10 km/s

A series of experiments has been performed on the Sandia Hypervelocity Launcher to determine the performance limits of conventional Whipple shields against representative 0.8 g aluminum orbital debris plate-like fragments with velocities of 7 and 10 km/s. Supporting diagnostics include flash X-rays, high speed photography and transient digitizers for timing correlation. Two Whipple shield designs were tested with either a 0.030 cm or a 0.127 cm thick front sheet and a 0.407 cm thick backsheet separated by 30.5 cm. These two designs bracket the ballistic penetration limit curve for protection against these debris simulants for 7 km/s impacts.

Ang, J. A.↗

Concept definition study for an extremely large aerophysics range facility

The development of a large aerophysical ballistic range facility is considered to study large-scale hypersonic flows at high Reynolds numbers for complex shapes. A two-stage light gas gun is considered for the hypervelocity launcher, and the extensive range tankage is discussed with respect to blast suppression, model disposition, and the sabot impact tank. A layout is given for the large aerophysics facility, and illustrations are provided for key elements such as the guide rail. The paper shows that such a facility could be used to launch models with diameters approaching 250 mm at velocities of 6.5 km/s with peak achievable accelerations of not more than 85.0 kgs. The envisioned range would provide gas-flow facilities capable of controlling the modeled quiescent atmospheric conditions. The facility is argued to be a feasible and important step in the investigation and experiment of such hypersonic vehicles as the National Aerospace Plane.

Swift, H.↗

The ballistic range - Its role and future in aerothermodynamic testing

Aerothermodynamic testing requirements for future missions are reviewed, and the ballistic range testing capabilities necessary to meet these requirements are outlined. The four issues of velocity, chemical scaling, cost analysis of ballistics facilities is presented. It is concluded that modern instrumentation and a launcher of 5 to 10 cm diameter can meet the requirements and be cost effective. Finally, recommendations for upgrading existing facilities and instrumentation to meet the needed ballistic range test capability in a cost efficient manner are presented.

Chapman, Gary T.↗

The influence of lunar propellant production on the cost-effectiveness of cislunar transportation systems

It is well known that propellants produced at the points of destination such as the Moon or Mars will help the economy of space transportation, particularly if round trips with a crew are involved. The construction and operation of a lunar base shortly after the turn of the century is one of the space programs under serious consideration at the present time. Space transportation is one of the major cost drivers. With present technology, if expendable launchers were employed, the specific transportation costs of one-way cargo flights would be approximately 10,000 dollars/kg (1985) at life-cycle cumulative 100,000 ton payload to the lunar surface. A fully reusable space transportation system using lunar oxygen and Earth-produced liquid hydrogen (LH2) would reduce the specific transportation costs by one order of magnitude to less than 1000 dollars/kg at the same payload volume. Another case of primary interest is the delivery of construction material and consumables from the lunar surface to the assembly site of space solar power plants in geostationary orbit (GEO). If such a system were technically and economically feasible, a cumulative payload of about 1 million tons or more would be required. At this level a space freighter system could deliver this material from Earth for about 300 dollars/kg (1985) to GEO. A lunar space transportation system using lunar oxygen and a fuel mixture of 50 percent Al and 50 percent LH2 (that has to come from Earth) could reduce the specific transportation costs to less than half, approximately 150 dollars/kg. If only lunar oxygen were available, these costs would come down to 200 dollars/kg. This analysis indicates a sizable reduction of the transportation burden on this type of mission. It should not be overlooked, however, that there are several uncertainties in such calculations. It is quite difficult at this point to calculate the cost of lunar-produced O and/or Al. This will be a function of production rate and life-cycle length. In quoting any cost of this nature, it is very important to state the cumulative transportation volume, since this is a very sensitive parameter. Nevertheless, cost models must be developed now to understand fully the interdependencies of a large number of parameters and to provide the best possible data for planning purposes. Without such data, mission modes and vehicle designs or sizes cannot be selected intelligently.

Koelle, H. H.↗

Electromagnetic launch of lunar material

Lunar soil can become a source of relatively inexpensive oxygen propellant for vehicles going from low Earth orbit (LEO) to geosynchronous Earth orbit (GEO) and beyond. This lunar oxygen could replace the oxygen propellant that, in current plans for these missions, is launched from the Earth's surface and amounts to approximately 75 percent of the total mass. The reason for considering the use of oxygen produced on the Moon is that the cost for the energy needed to transport things from the lunar surface to LEO is approximately 5 percent the cost from the surface of the Earth to LEO. Electromagnetic launchers, in particular the superconducting quenchgun, provide a method of getting this lunar oxygen off the lunar surface at minimal cost. This cost savings comes from the fact that the superconducting quenchgun gets its launch energy from locally supplied, solar- or nuclear-generated electrical power. We present a preliminary design to show the main features and components of a lunar-based superconducting quenchgun for use in launching 1-ton containers of liquid oxygen, one every 2 hours. At this rate, nearly 4400 tons of liquid oxygen would be launched into low lunar orbit in a year.

Snow, William R.↗

National launch system overview with focus on cargo transfer vehicle

As a result of the Augustine Committee's recommendation to the National Space Council, NASA, and the DOD have embarked on a joint program to provide the nation with a new capability for transporting payloads into space. The National Launch System (NLS) consists of a family of modular launch vehicles, combining elements of current launchers (Titan and Shuttle) with newly developed components. This family consists of (1) NLS-1 (a vehicle capable of delivering 80 k to SSF), (2) NLS-2 (a vehicle capable of delivering 50k to LEO), and (3) NLS-3 (a vehicle capable of delivering 20 k to LEO). Management of the program is shared between the two agencies with a Joint Program Office carrying out the level 2 management and integration function while both the NASA and Air Force field organizations are charged with the various development and operational responsibilities.

Buchanan, Harry↗

ASUR

The Ecole Polytechnique Feminine (EPF) is a French engineering school for women. The students who presented the project at the Summer Conference are in the fourth year of a five year program. For the second time, the EPF worked on an aeronautical project with the Ohio State University. This year, the theme was to design a hypersonic carrier aimed to launch an orbiter at Mach 6, a range of 375 miles and an altitude of 95,000 ft. The plane was called ASUR which in French means the blue sky, the same sky that links our countries across the ocean. Moreover, ASUR is an anagram of USRA. This work benefits from work on reusable hypersonic aircraft in Europe, and especially on two of them: STAR-H and Sanger. STAR-H is a French project. This hypersonic aircraft would replace Ariane 5 in launching a shuttle smaller than Hermes. Sanger is a German project. Its objective is to launch a manned shuttle called HORUS, but Ariane 5 would be kept for heavy cargo launches. These two projects are in competition in Europe to be a launcher of the European Space Agency.

Source record↗

The first mission to Mars

NASA's first mission to Mars used an Atlas-Agena D launcher, which left Cape Canaveral on November 28, 1964, to place a Mariner probe capable of telemetering back photographs of the Martian surface. After an 8-month flight of 135 million miles, the spacecraft encountered Mars only 500 miles off the aiming point 6000 miles from the Martian surface. Attention is given to NASA-JPL's solving of problems arising after Mariner's separation from the Agena upper stage, using two competing investigative teams.

James, J. N.↗

Establishing the infrastructure - An integrated Space Transportation System

A discussion is presented concerning the various transfer vehicle/propulsion systems that are currently under consideration within the egis of the NASA Space Exploration Initiative for the establishment of an infrastructure for lunar base construction and Mars exploration. Cryogenically fueled and nuclear propulsion alternatives are considered, as well as such advanced concepts as that employing nuclear-electric propulsion and artificial gravity and a solar-electric propulsion zero-gravity concept. Mars lander and earth-to-LEO launcher concepts are also noted.

Huber, W. G.↗

Environmental monitoring of Space Shuttle launches at Kennedy Space Center - The first ten years

Space Shuttle launches produce local environmental effects through the generation of a launcher exhaust plume that in turn produces acidic depositions and acute vegetation damage in the near-field environment; fish kills have also been noted in the lagoon or impoundment near each of the launch pads. Repeated launches lead to cumulative changes in plant community composition and structure, and temporary decreases in pH due to acidification increases metal availability in soil microcosms and surface waters. Direct effects on terrestrial fauna include the mortality of birds, mammals, amphibians, and reptiles in the near-field area.

Schmalzer, Paul A.↗

Initiation of combustion in the thermally choked ram accelerator

The methodology for initiating stable combustion in a ram accelerator operating in the thermally choked mode is presented in this paper. The ram accelerator is a high velocity ramjet-in-tube projectile launcher whose principle of operation is similar to that of an airbreathing ramjet. The subcaliber projectile travels supersonically through a stationary tube filled with a premixed combustible gas mixture. In the thermally choked propulsion mode subsonic combustion takes place behind the base of the projectile and leads to thermal choking, which stabilizes a normal shock system on the projectile, thus producing forward thrust. Projectiles with masses in the 45-90 g range have been accelerated to velocities up to 2650 m/sec in a 38 mm bore, 16 m long accelerator tube. Operation of the ram accelerator is started by injecting the projectile into the accelerator tube at velocities in the 700 - 1300 m/sec range by means of a conventional gas gun. A specially designed obturator, which seals the bore of the gun during this initial acceleration, enters the ram accelerator together with the projectile. The interaction of the obturator with the propellant gas ignites the gas mixture and establishes stable combustion behind the projectile.

Bruckner, A. P.↗